Oil retention and crankcase pressure control system for refrigerant compressors



Oct. 21, 1969 w, CHENEY ErAL 3,473,730

AND CRANKCASE PRESSURE TROL SYSTEM OIL RETENTION FOR REFRI E AN 0MP SO Filed O. 19

3,473,730 011. RETENTION AND CRANKCASE PRES- SURE CONTROL SYSTEM FOR REFRIG- ERANT COMPRESSORS Lawrence W. Cheney, Sidney, and James A. Short, Anna, Ohio, assignors to Copeiand Refrigeration Corporation Filed Dec. 15, 1967, Ser. No. 690,820 Int. Cl. F041) 39/02 US. Cl. 230-406 2 Claims ABSTRACT OF THE DISCLOSURE In a refrigeration motor-compressor of the hermetic type containing an electric motor compartment, and a crankcase compartment separated by a vertical partition, a passage for refrigerant returned for recom-pression leads from the motor compartment to the intake manifold via a riser passage containing an eduction pipe which at the bottom is connected to the top of the crankcase compartment. A valve is provided at the top of the eduction pipe and is spring-biased to a position such that communication is substantially unobstructed between the crankcase and compressor inlet. The valve consists of a disc having a small central orifice and a plurality of surrounding orifices of greater area.

BRIEF SUMMARY OF THE INVENTION The present invention relates to means for controlling pressure relationships between the oil sump-crankcase and the inlet of a hermetic refrigeration motor-compressor, and for controlling the migration of lubricant, constituting an improvement upon the invention disclosed in Neubauer Patent 3,123,287. Said Neubauer patent discloses apparatus which effects a substantial improvement in preventing the unwanted migration of oil from the crankcase. In accordance with the teaching of such patent, a check valve is located in and near the top of the crankcase chamber and arranged so that during normal running conditions it maintains a substantial area of intercommunication between the crankcase and the inlet of the compressor, through a plurality of ports of predetermined size and thence through an eduction pipe which opens into and is influenced by the inlet gas stream, while when the valve is closed due to a rise in crankcase pres sure such as is caused by foaming, the valve closes, but a restricted communication past the valve is maintained. An object of the present inventio is to remove such valve entirely from the crankcase, and to so position the valve that no oil can be thrown into the valve intake ports during operation of the compressor, and a shielded low velocity area is provided below the valve, whereby any oil which enters the eduction pipe can drain back into the crankcase and cannot be blocked by the valve structure or by the velocity or direction of flow in the valve ports.

Other objects and advantages will become apparent upon consideration of the present disclosure in its entirety.

IN THE DRAWING FIGURE 1 is a fragmentary vertical sectional view of a refrigeration motor compressor unit incorporating the present invention;

FIGURE 2 is a horizontal sectional plan view taken substantially on the line IIII of FIGURE 1, and looking in the direction of the arrows;

FIGURE 3 is a diametric vertical section of the crankcase vent valve assembly on a larger scale; and

FIGURE 4 is a plan view of the valve disc.

'11 hired States Patent 3,473,730 Patented Oct. 21, 1969 "ice DETAILED DESCRIPTION Referring now to the drawing, reference character 10 designates generally the body of a reciprocating motorcompressor shown as of the twin cylinder accessible hermetic type wherein the crankshaft 12 is rotatable on a horizontal axis by an electric motor assembly 14 housed in a compartment 15 which is located beside and slightly higher than the crankcase compartment 20 and separated therefrom by an upright partition 18.

The inlet (not shown) through which refrigerant for re-compression is returned to the motor compressor assembly opens into the motor compartment 15 and any oil contained in such returning refrigerant tends to settle to the bottom of compartment 15 from which it returns to the oil sump defined by the bottom of the crankcase 20 through a port 19 containing a check valve assembly 22. Check valve assembly 22 is preferably constructed as shown in the aforementioned prior Patent 3,123,287, so that during normal running it is open for return of oil, but closes in event of a substantial rise in pressure in the crankcase.

Gaseous inflowing refrigerant is conducted from compartment 15 via an inclined side passage 25 to a riser passage 26 located in the cylinder section of the body and which opens upwardly into the intake manifold or head chamber 30. Eduction riser pipe 33 is fitted as by means of nipple 34 into the otherwise closed top wall 35 of the crankcase and extends upwardly within the riser passage 26 carrying at its top near the upper extremity of the riser passage but still within the high velocity area thereof a check valve assembly generally designated 36.

Check valve assembly 36 contains a transversely arranged vertically displaceable valving disc 38 which is biased downwardly by a compression spring 40. The cylindrical valve body 42 which contains the disc and spring has a central top outlet port 44 which opens in the direction of gas flow. The outlet is surrounded by a depending annular seat-defining wall 45. As shown in FIGURE 4, the valve disc 38 has a restricted central outlet port 50 and a plurality of larger outspaced outlet ports 52, an imperforate substantially annular area 54 being left between the orificed areas 50 and 52 and all of these parts and areas of the valve assembly being concentric, the area 54 being adapted to bear against the annular seat 45 when the disc is raised thereagainst, so that at such time communication between the crankcase compartment 20 and intake chamber 30 is limited to the restricted orifice 50. When the valve disc is in its lowermost position spaced from the seat 45, the ports 52 in the disc provide a substantial area of communication, as will be apparent.

Upon a substantial rise of crankcase relative pressure such as occurs under certain conditions at startup, or if foam should rise to engage the disc, the disc is lifted against the seat 45, substantially restricting the communication and limiting the escape of oil but permitting the crankcase pressure to equalize subsequently, so that as pressure and foaming subside the disc may move down to thereby establish a substantial area of communication via ports 52 and enable the effective maintenance of a desirably reduced relative crankcase pressure.

Any oil which is thrown or finds its way into the eduction pipe can run down its walls and return to the crank case through its unobstructed connection therewith, and the tube shields the higher velocity areas in the valve mechanism against the access of oil. The passages in the valve are entirely vertical as well as spaced from the crankcase and from splashed and thrown oil and any foam must rise much higher before reaching the higher velocity ported areas. It has been found in preliminary testing of an experimental compressor constructed as 3 herein disclosed that a substantial further reduction of oil migration is attained.

What is claimed is:

1. -In a refrigeration compressor having an inlet passage and a crankcase compartment containing an oil sump and substantially isolated from the inlet passage, a substantially upright pressure control conduit having an inlet communicating with an upper portion of said crankcase compartment and having an outlet end in said compressor inlet passage and spaced from the crankcase, a valve mounted on the outlet end of said conduit to control flow of fluid therethrough and movable between a substantially non-restricting position with respect to flow through said conduit and a position to throttle such flow in response to changes in relative efiective pressures in said crankcase compartment, and in said passage at the outlet of the valve, said inlet passage surrounding said valve and the valve outlet in eductive relation therewith.

2. A compressor as defined in claim 1 wherein said valve has outlet means opening in the direction of flow through said passage and through Which outlet means flow takes place in the same direction in both positions of the valve.

References Cited UNITED STATES PATENTS ROBERT M. WALKER, Primary Examiner 

